In recent years, solid image pickup devices that photo-electrically convert subject images formed by an image pickup optical system have come to be widely used for video cameras and still cameras. Further, as a small-sized camera module, such solid image pickup devices are mounted on portable terminals which are small and thin type electronic devices, such as portable telephones and PDAs (Personal Digital Assistant).
As an image pickup unit in such solid image pickup devices, a CCD (Charge Coupled Device) type image sensor, a CMOS (Complementary Metal Oxide Semiconductor) type image sensor, or the like is used. In these solid image pickup apparatuses, an image pickup unit is adhesively fixed to a board in a state of a bare chip, and the image pickup device and the board are electrically connected by bonding wires.
A solid image pickup unit in which an image pickup unit is adhesively fixed to a board, as described above, is disclosed in which plural protrusions are formed on a board, and the image pickup unit is adhered with a support by the protrusions so as to reduce deformation of the image pickup unit caused by adhesion with a board having insufficient flatness (for example, refer to Patent Document 1, that is, Japanese Laid Open Patent Document TOKKAI No. 2005-129721).
Cameras and camera modules employing the above described solid image pickup device have a purpose to obtain a higher image quality. Therefore, an image pickup unit with a large number of pixels which are disposed in a high density with a small pixel pitch has come to be adopted for these cameras and camera modules.
With this high pixelization of this kind of image pickup unit, it is necessary that the light receiving surface of an image pickup unit disposed at an image forming plane of an image pickup optical system is flat and disposed accurately orthogonal to the optical axis of the image pickup optical system. For example, in the case where the pixel pitch of the image pickup unit δ=2.2 μm and F number of the image pickup optical system F=2.8, with an assumption that the focal depth is 2Fδ, the focal depth is 12.32 μm. Accordingly, the light receiving surface is needed to be disposed such that the deviation amount of the most peripheral diagonal part of the image pickup unit surface is within 12.32 μm with respect to the plane orthogonal to the optical axis at the point where the image pickup unit surface and the optical axis intersect with each other. That is, the focal depth on the image plane side is extremely small, and setting of the image pickup unit surface with respect to the optical axis of the image pickup optical system requires an extremely high accuracy.
Although the solid image pickup device disclosed in the above Patent Document 1 can reduce the distortion of the image pickup unit surface, the board to which the image pickup unit is adhered is formed by a mold, and accordingly, it is difficult to accurately conform the respective heights of the protrusions formed on the board. Therefore, it is difficult to produce a solid image pickup device in which the image pickup unit surface is stably in a desired direction with respect to the surface of the substrate. Further, mold processing and management of exact forming conditions are required, and particularly, the cost of mold processing is increased.
Further, in the case of COB (Chip In Board) mounting of an image pickup unit in a bare chip state on a print board in order to make the solid image pickup device further thin, the structure disclosed in the Patent Document 1 cannot be applied.
To solve problems as described above, an object of the invention is to provide a thin-type solid image pickup device which can be manufactured such that, in the case of COB (Chip In Board) mounting of an image pickup unit in a bare chip state on a print board, it is possible to accurately conform the respective heights of the protrusions formed on the substrate at a low cost, and it is also possible to make the image pickup unit surface stably in a desired direction with respect to the surface of the board.